1. Field of the Invention
The present invention relates to a particle beam irradiation system. More particularly, the present invention relates to a particle beam irradiation system suitably used in not only inspection employing equipment of Positron Emission Tomography (hereinafter abbreviated to “PET”) for producing a radioactive isotope (RI), e.g., fluorine 18, which is employed in a radioactive drug (hereinafter referred to as a “PET drug”) and applied to a patient (subject) going to take the inspection, but also in treatment of cancers.
2. Description of the Related Art
As known in the art, proton-beam cancer treatment equipment used for treatment of cancers employs an ion beam accelerating system including a linear accelerator (linac) having an acceleration capability in the range of several to 10 MeV as a beam introducing unit and a synchrotron, or an ion beam accelerating system including a cyclotron. On the other hand, in equipment for producing the PET drug, a cyclotron (or a linear accelerator) having an acceleration capability in the range of 7 to several 10's MeV is employed to accelerate a proton beam and irradiate the accelerated beam against a target, thereby producing the radioactive isotope capable of radiating positrons.
Hitherto, a facility employing the proton-beam cancer treatment equipment and a facility employing the PET drug production equipment have been separately constructed corresponding to the fact that application fields of those equipments have been separated into treatment and diagnosis of cancers. With recent widespread use of the PET equipment and the proton-beam cancer treatment equipment, however, a demand has increased for a treatment plan capable of diagnosing the treatment effect with higher accuracy and further increasing the treatment effect. Such a demand has brought about a tendency to construct the proton-beam cancer treatment equipment and the PET equipment in combined layout. Because the half-life period of a RI (e.g., fluorine 18) used in the PET drug is very short, the PET equipment is required to include the PET drug production equipment, i.e., RI production equipment.
Patent Document 1; JP,A 2001-85200 discloses examples of combined layout of the proton-beam cancer treatment equipment and the RI production equipment. According to Patent Document 1, in a treatment system including a linear accelerator and a synchrotron, an ion beam extracted from the linear accelerator is introduced to the RI production equipment, thereby producing a RI. More specifically, the treatment systems disclosed in Patent Document 1 comprise the linear accelerator, the RI production equipment, and the synchrotron. The treatment system further comprises a switching magnet serving as a beam path switching unit and disposed downstream of the linear accelerator. The switching magnet introduces the ion beam extracted from the linear accelerator to the synchrotron or the RI production equipment. When the ion beam is irradiated to a patient, the ion beam extracted from the linear accelerator is introduced to the synchrotron by the switching magnet. The ion beam is accelerated in the synchrotron so as to have a preset level of energy and then irradiated to the patient. When the RI is produced, the ion beam extracted from the linear accelerator is introduced to the RI production equipment by the switching magnet and then irradiated to a target in the RI production equipment.
In a particle beam irradiation system disclosed in the above-cited Patent Document 1, the ion beam extracted from the linear accelerator is introduced to the synchrotron or the RI production equipment with the switching operation of the switching magnet.